Home and building automation makes use of wireless networks. Over the past years, numerous types of networks have been proposed and are being used. As an example, ZigBee is a low-cost, low-power, wireless mesh network standard. The low cost allows the technology to be widely deployed in wireless control and monitoring applications. Low power usage allows longer life with smaller batteries. ZigBee is based on the IEEE 802.15.4 standard. Though low-powered, ZigBee devices often transmit data over longer distances by passing data through intermediate devices to reach more distant ones, creating a mesh network (i.e., a network with no high-power transmitter/receiver able to reach all of the networked devices). The decentralized nature of such wireless ad hoc networks makes them suitable for applications where a central node can't be relied upon.
In order for applications to communicate, they must be able to join the same network, i.e. get configured with network operational parameters, e.g. network identifier, operational channel, security key, etc. The mandatory or optional methods to exchange those parameters, also referred to as commissioning (procedure(s)), are defined in so-called application profiles. Furthermore, binding, i.e. application level control relationship, telling one device that its control data is to be sent to another device and/or that it shall accept control data from another device, is decided upon by matching input and output cluster identifiers, associated to an incoming or outgoing data flow in a device. Binding tables contain source and destination pairs. ZigBee is available as two feature sets, ZigBee PRO and ZigBee and they define how ZigBee mesh networks operate. ZigBee PRO, the most widely used specification, is optimized for low power consumption and to support large networks with thousands of devices. ZigBee PRO proposes several application profiles that could coexist in the same area. However, at the moment, there are some incompatibilities which prevent nodes from different profiles to form a single network.
Two of the several ZigBee public application profiles will be discussed here in more detail, because they compete for the same market space: the consumer market. ZigBee Home Automation (ZHA) is an industry global standard helping to create smarter homes that enhance the comfort, convenience, security and energy management for the consumer. Furthermore, ZigBee Light Link (ZLL) gives the lighting industry a global standard for interoperable and very easy-to-use consumer lighting and control products. It allows consumers to gain wireless control over all their LED fixtures, light bulbs, via timers, remotes and switches. An emblematic non-interoperability case is represented by ZHA profile and ZLL profile devices. The main difference here is the different nature of the profiles involved. Namely, ZHA is built around a central coordinator, centrally managing the network joining process, while ZLL devices can operate in a distributed network taking advantage of a so-called “Touchlink” mechanism to locally add components and manage the lighting network.
The task of configuring devices and networks to achieve the needs of the specific installation is known as commissioning. In its broadest sense, commissioning encompasses a wide range of tasks, including a survey of the radio and physical environment, the placement of devices, configuration of parameters, application binding, optimization of network and device parameters, and testing and verification of correct operation. Often, non- and semi-technical issues need to be considered, including the skills and workflow practices of the installer, ease of identification and accessibility of devices, and interoperability and coexistence with other wireless or wired systems. While consideration for commissioning is often focused on the installer, the ability to easily configure and commission ZigBee systems during development and testing, as well as field trials, can also significantly speed up the development and product delivery to market. Moreover, ease of commissioning is also important for the do-it-yourself consumer market.
More specifically, the commissioning process may involve a number of steps, comprising network creation, joining/discovery of an active network, address assignment, security key exchange, finding and binding between devices, and application layer configuration (e.g. of reporting intervals, etc.).
Three different commissioning modes are typically discussed with in the ZigBee Alliance. The first, A-mode (automatic mode), involves automatic commissioning of devices. The A-mode generally allows for minimal (or no) human intervention. The second, E-mode (easy mode), involves the use of buttons or other physical mechanisms on devices to direct devices during commissioning. The E-mode allows for simple end-user or professional installer commissioning. It usually targets small installations (size: typical home). The third, S-mode (system mode), involves the use of external tools and is typically used by expert installers. The S-mode represents the most complex form of commissioning and includes the highest level of human intervention. It usually targets larger installations such as commercial premises and high-end residential environments. Furthermore, the S-mode is a centralized commissioning which is a means for a (central) device to perform or control or influence commissioning on/of other devices. This type of commissioning is also being referred to as Gateway-, or Tool-commissioning. The central device can be a gateway, a home controller or a commissioning tool that is typically connected to a graphical user interface. It is able to configure bindings and reporting on other devices in the network. The central device is not required to perform ZigBee Coordinator role. In fact, it can be a ZigBee Router as well. The device in a ZHA network with this functionality is defined as Commissioning Director (CD).
Current specifications for ZHA profiles define two different main commissioning modes, namely EZ-mode commissioning (e.g. push button commissioning) and centralized commissioning (e.g., aka Gateway, Tool or S-mode Commissioning), wherein EZ-Mode and centralized commissioning are complementary and fully compatible.
In the same vein, the ZLL profile specification (as disclosed in docs-zll-zigbee-light-link-zll-profile-specification, ZigBee document number 11-0037) provides as preferred commissioning mechanism a Touchlink (TL) commissioning. The ZLL system benefits from a simplified installation method in order to appeal to the consumer market. Touchlink minimizes user participation, allowing off-the-shelf products to be quickly and easily installed by the consumer. The security model of Touchlink requires physical proximity between the devices which shall Touchlink together, thus assisting network discovery and selection. It also is best suited for devices with very limited or no (physical) user interface (UI) means, since on ZLL target the Touchlink is not required to be triggered by other means than the over-the-air exchange (in proximity). Touchlink removes the need for a ZigBee Coordinator in the network formation and join processes. The method uses a special commissioning application (based on a ZLL commissioning cluster) which is run on the nodes, and utilizes the Inter Personal Area Network (Inter-PAN) frames, allowing for information exchange between devices not yet operational on the same network. The node that initiates the network formation/join operation is known as the ‘initiator’—this node will often be a remote control unit but could be another node, e.g. a switch, a sensor or even a lamp. Touchlink simply requires the initiator node to be brought close to the node to be included in the network and the commissioning to be started (e.g. by pressing a button). The node that is contacted by the initiator to perform a network formation or join operation is known as the ‘target’.
Current ZigBee specifications describe for each public application profile the detailed steps needed for a non-connected device to reach its normal operational state. Considering the number and complexity of tasks generally involved in the commissioning phase, it is easy to see the value of a single commissioning tool to set up devices belonging to different ZigBee public application profiles.
Since each ZigBee public application profile has been conceived for addressing different needs and scenarios, the respective existing commissioning procedures present some differences that do not allow devices belonging to different profiles to communicate to each other.
Today, the step related to the creation of the network, in case of a factory new device, presents a relevant issue for both profiles. ZLL target devices need to communicate with an initiator which guarantees the distributed network inception via Inter-PAN based commands, while ZHA devices—for the same task—rely on the presence of a central coordinator, absent in the ZLL network topology. For these reasons, the current commissioning procedures are not applicable in any context in which a ZLL router wants to have control over a ZHA end device and vice versa, especially if both devices are non-connected yet and a network is absence.
The main consequence of these gaps is that currently available commissioning tools can only be used to set up a system in which all the devices belong to the same ZigBee public profile.
In the ZigBee Building Automation application profile specifications, a commissioning tool is defined, which may have the ability to create its own temporary commissioning network, pull the joiner to that, and instruct the joiner to join another network subsequently. However, all these functionalities require the joiner to implement the ZCL commissioning cluster.